This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications JP2001-335662 filed on Oct. 31, 2001, JP2001-397205 filed on Dec. 27, 2001 and JP2002-97684 filed on Mar. 29, 2002, the entire contents of which are incorporated herein by reference.
The present invention relates to a compact selfballasted fluorescent lamp and a luminaire.
A compact selfballasted fluorescent lamp is composed of one integrated fluorescent arc tube whose discharge path is formed by crooked tubes and a housing for supporting the fluorescent arc tube. The housing has a bulb-base and accommodates a lighting circuit module for lighting the fluorescent arc tube.
In such a compact selfballasted fluorescent lamp, there is a great concern that the temperature rise within the housing during lighting causes a bad influence on the circuit components of the lighting circuit. In order to prevent the temperature rise within the housing caused by the heat of the lighting circuit module, it is known as a technique of filling synthetic resin in the space between the circuit board and the housing so as to contact them with each other, as disclosed in, e.g., the JP-A 57-50762.
In the conventional technique, synthetic resin is filled in the space between the circuit board and the inner wall of the housing, contacts the circuit components mounted on the circuit board and the inner wall of the housing. Thus heat of the lighting circuit module utilizing the electronic ballast is dissipated by conducting through the synthetic resin. Hereby, while the lighting efficiency of the fluorescent arc tube being improved, the temperature rise in the lighting circuit module could be depressed. Further, it is not necessary to define an air hole in a housing and to use an expensive glove having high heat resistance either.
However, as the compact selfballasted fluorescent lamp is high-powered and miniaturized the space for accommodating the luminaire becomes much more narrow. As a result, the temperature within the housing rises further. In case of an inverter circuit, wherein the lighting circuit mounted in a compact selfballasted fluorescent lamp is composed of circuit components, some circuit components relatively vulnerable to heat are included in them. Thus, it is necessary to prevent overheating inside the housing by more efficiently dissipating heat in the housing in order to protect the circuit components. Furthermore, the practical specification of the synthetic resin for dissipating heat inside the housing has to be adopted in consideration of the heat resistance of the circuit board or circuit components. However, neither detailed analyses nor sufficient developments for making heat inside the housing not to defect the lighting circuit module have been proceeded.
The present invention has an object to provide a compact selfballasted fluorescent lamp which has a high reliability in the lighting circuit module by efficiently dissipating heat inside the housing, in consideration of dissolving the problems as described above.
A compact selfballasted fluorescent lamp according to the first aspect of the invention, comprising
a fluorescent arc tube forming a crooked discharge path, a housing comprised of a first end portion open to be fit thereon with a bulb-base (hereinafter referred to as bulb-base applying end portion), a middle portion and a second end portion open to be mounted thereto with the fluorescent arc tube (hereinafter referred to as fluorescent arc tube module applied portion), a lighting circuit module accommodated in the housing, the unit being provided with a circuit board and two or more circuit components mounted on the circuit board for constituting a lighting circuit for lighting the fluorescent arc tube, and a thermal conductor having a thermal conductivity of 0.1 W/(mxc2x7K) or more, which is filled in the housing, extending upwards from a components mounting side of the circuit board of the lighting circuit module and contacting with the inner wall of the housing lying on the side of the first end portion of the housing, thereby covering at least one of the circuit components of the lighting circuit.
The thermal conductor is desirable to have heat conductivity higher than air, and have moderate fluidity at the time of filling the thermal conductor in the housing.
In order to efficiently dissipate heat of the lighting circuit module developed by itself or conducted from the fluorescent arc tube, the thermal conductor filled in the housing in proximity to the circuit components developing a large amount of heat or contacted with a part of or whole surface of the circuit component, and also it is desired to contact with the housing inner wall as large an area as possible.
The circuit components subject to the heat dissipation by the thermal conductor may be not only those developing a large amount of heat but also those having low heat resistance. That is, it is because the thermal conductor has a function to prevent heat affection on the circuit components having low heat conductor.
A housing for accommodating the lighting circuit module for lighting the fluorescent arc tube is made of synthetic resin or a metal with thickness of 0.5 to 3 mm in general.
An area surrounding the circuit components of the lighting circuit module inside the housing is relatively large. Accordingly, the thermal conductor is able to contact with the housing inner wall over relatively large area, so that it is able to conduct and dissipate heat developed inside the housing to the outside.
In order to conduct heat from the circuit components to the housing efficiency, it needs to enhance the thermal conductivity of the thermal conductor. It was experimentally confirmed that it was able to efficiently lower the temperature inside the housing when the thermal conductor has a thermal conductivity more than 0.1 W/(mxc2x7K). As the thermal conductor having such thermal conductivity, for example, silicone resin or epoxy resin are suitable.
In case of an integrated crooked fluorescent arc tube, its cooked portions may have a semicircle shape or a horseshoe shape. Alternatively, adjacent two straight tubes of parallel-aligned two crooked tubes may be coupled through a coupling tube communicating with their sides near the respective tube ends in order to form a crooked discharge path.
In the compact selfballasted fluorescent lamp according to the first aspect of the invention, at least one of the circuit components mounted on the circuit board of the lighting circuit module is covered with the thermal conductor whose thermal conductivity is more than 0.1 W/(mxc2x7K), while the thermal conductor contacts with the inner wall of the housing, thereby it is able to efficiently dissipate heat developed by the circuit components via the thermal conductor.
A compact selfballasted fluorescent lamp according to the second aspect of the invention, comprising a fluorescent arc tube forming a crooked discharge path, a housing having a bulb-base applying end portion, a middle portion and a second end portion open to be mounted thereto with the fluorescent arc tube, a lighting circuit module accommodated in the housing, the unit being provided with a circuit board and two or more circuit components mounted on the circuit board for constituting a lighting circuit for lighting the fluorescent arc tube, and a thermal conductor filled in the housing in contacting with the inner wall of the housing, thereby covering some circuit components of the lighting circuit module, wherein the housing excepting the bulb-base applying end portion has an outer surface area per unit lamp power not exceeding 500 mm2/W.
The term xe2x80x9cbulb-base fitting portion of the housingxe2x80x9d means a cylindrical portion formed on one end of the housing, whereon the bulb-base is to be fit.
When the housing excepting the bulb-base applying end portion has an outer surface area per unit lamp power more than 500 mm2/W, it suffers affections of heat developed by the lighting circuit module itself and the fluorescent arc tube. However, in such a conventional compact selfballasted fluorescent lamp wherein a whole surface are of the housing is large, the heat spreads within the housing, while it is dissipated from the housing with a very large surface. Thus, the temperature in the housing is less apt to rise so high to deteriorate the lighting circuit module. Therefore, it would not be required to fill the thermal conductor in the housing for efficiently dissipating heat inside the housing differently from such a conventional technique.
In the compact selfballasted fluorescent lamp according to the second aspect of the invention, even though the compact selfballasted fluorescent lamp is miniaturized but high-powered so as that the housing excepting the bulb-base fitting portion has an outer surface area per unit lamp power not exceeding 500 mm2/W, the lighting circuit module is less deteriorated from the heat affection since the thermal conductor filled in the housing which covers at least one of the circuit components of the lighting circuit module and contacts the inner wall of the housing efficiently dissipates heat developed by the lighting circuit module and the fluorescent arc tube.
In addition to the feature of the second aspect of the invention, in the compact selfballasted fluorescent lamp according to the third aspect of the invention, the thermal conductor contacts the inner wall of the housing more than 30% thereof.
When the area that the thermal conductor contacts with the housing inner wall is not more than 30% of the inner wall of the housing, it is difficult to sufficiently dissipate heat, and the amount of heat conducted from the fluorescent arc tube exceeds the amount of heat developed by the lighting circuit module, so that the temperature in the housing rises even though the thermal conductor is filled in the housing. In order to provide a lighting circuit module with a high reliability by restraining occurrences of failures in the lighting circuit module by the heat affections, it is necessary make the contacting area to 30% or more of the inner wall of the housing.
According to the third aspect of the invention, the compact selfballasted fluorescent lamp is able to reliably dissipate heat in the housing through the thermal conductor and the housing.
In addition to the feature of any one of the first to third aspects of the invention, the compact selfballasted fluorescent lamp according to the fourth aspect of the invention is characterized by that the thermal conductor of the compact selfballasted fluorescent lamp is curable and has a viscosity of 10 to 500 Paxc2x7s in being filled in the housing.
It is desirable for manufacturing the compact selfballasted fluorescent lamp that the thermal conductor is filled in the housing after that the lighting circuit module has been accommodated in the housing. In this case, in order to fill up the thermal conductor in narrow gaps between the circuit components arranged densely and the housing inner wall, the thermal conductor is desired to have a moderate fluidity capable of flowing into the narrow gaps at the time of filling.
In order to satisfy such a condition, it was experimentally confirmed that the viscosity of the thermal conductor should be not exceeding 500 Paxc2x7s in being filled in the housing. Furthermore, the thermal conductor flows out of the gap formed between the circuit board and the fluorescent arc tube holder before it is cured if the viscosity of the thermal conductor is low. So, it was experimentally confirmed that the flowing of the thermal conductor could be prevented if the thermal conductor has the viscosity more than 10 Paxc2x7s.
The viscosity of the thermal conductor is defined in the Japanese Industrial Standards JIS-K 6300.
In the compact selfballasted fluorescent lamp according to the fourth aspect of the invention, it is able to fill up the thermal conductor in the space between the circuit components and the housing inner wall without leaving any gap, and also it is able to prevent the thermal conductor from flowing out of the gap between the circuit board and the fluorescent arc tube holder.
In addition to the feature of any one of the first to fourth aspects of the invention, the compact selfballasted fluorescent lamp according to the fifth aspect of the invention is characterized by that the hardness of the thermal conductor of the compact selfballasted fluorescent lamp is not more than 100 JIS-A after cured.
The cured thermal conductor after filled in the housing expands by heat developed by the fluorescent arc tube and the lighting circuit module while lighting, and then it presses the circuit components, circuit board, and housing. Thus, it was found that the thermal stress causes the problem such as a crack. So, it was experimentally found that it is able to prevent the thermal stress of the expanded thermal conductor to the circuit components, circuit board, and housing by setting the hardness of the thermal conductor after cured not more than a predetermined value.
The hardness of the thermal conductor is defined in the Japanese Industrial Standards JIS-K 6253.
In the compact selfballasted fluorescent lamp according to the fifth aspect of the invention, since the hardness of the thermal conductor after cured is not more than 100 JIS-A, the thermal stress of the thermal conductor applied to the circuit components is lessen in spite of the thermal expansion of the thermal conductor, so as not to cause the problem to the circuit components.
In addition to the feature of any one of the first to fifth aspects of the invention, the compact selfballasted fluorescent lamp according to the sixth aspect of the invention is characterized by that the thermal conductor contains a filler more than 0.1% by mass, which is made of at least one of oxide, nitrogen oxide, and oxide hydrogen of one element among a group consisting of aluminum (Al), silicon (Si), titanium (Ti), and magnesium (Mg).
As an additive for enhancing the thermal conductivity of the thermal conductor, for instance, there are oxides such as Al2O3, TiO2, SiO2, MgO, nitrides such as AlN, Si3N4, and hydrates such as Al2O3-nH2O, TiO2-nH2O, Mg(OH)2.
In the compact selfballasted fluorescent lamp according to sixth aspect of the invention, an amount of heat developed by the fluorescent arc tube increases with a miniaturization of the fluorescent arc tube, and the temperature in the housing accommodating the lighting circuit module increases as the miniaturization of the housing. However, by adding more than 0.1% by mass of fillers made of at least one of oxide, nitrogen oxide, and oxide hydrogen of one element among a group which consists of aluminum (Al), silicon (Si), titanium (Ti), and magnesium (Mg) to the thermal conductor which is filled in the housing, the thermal conductivity of the thermal conductor in the housing heated to high temperatures will be better, so that it is able to efficiently dissipate heat from the circuit components and the fluorescent arc tube and also able to control to prevent the heat affection to the lighting circuit.
In addition to the feature of any one of the first to sixth aspects of the invention, the compact selfballasted fluorescent lamp according to the fifth aspect of the invention is characterized by that the thermal conductor contains oligomers not more than D10 in the total content not exceeding 5000 ppm.
The term xe2x80x9cconstituents not more than D10xe2x80x9d means those of monomers which stay in not combined completely. When these constituents are used as the thermal conductor, these are easily emitted as impurity gas from silicone resin which becomes high temperature during the operation. When the total content of the oligomer constituents not more than D10 that are monomers staying in being not combined completely is more than 5000 ppm, the impurity gas is generated more, and constituents gasified during the lamp operation adhere to a glass glove, so that the light transmitting efficiency of the fluorescent arc tube is deteriorated. When the total content of the oligomer constituents not more than D10 is not exceeding 5000 ppm, although constituents with less amount of monomers are easily gasified, the light transmitting efficiency of the fluorescent arc tube is not deteriorated since the oligomer constituents which adhere to the glass glove are not much. Accordingly, the total content of the oligomer constituent should not exceed 5000 ppm. It is desirable to have less oligomer constituents, since the less it contains the oligomer constituents, the less gases are generated during the lighting operation. However, the less it contains the oligomer constituents, the more the thermal conductor will be expensive, so that it is desirable to contain the oligomer constituent not more than D10 in the thermal conductor will be about 2000 ppm.
In the compact selfballasted fluorescent lamp according to the seventh aspect of the invention, by specifying the monomer and a total content of the oligomer constituent of the thermal conductor which is filled in the housing heated to high temperature, it is able to control the amount of gas generated from the oligomer constituents of the thermal conductor.
In addition to the feature of any one of the first to seventh aspects of the invention, the compact selfballasted fluorescent lamp according to the eighth aspect of the invention is characterized by that the thermal conductor is filled in the housing so as to contact with at least a metal portion of the bulb-base.
Since at least a node of the bulb-base is made of a metal, the thermal conductivity is relatively high. Therefore, it is able to dissipate heat effectively by conducting heat in the housing via the thermal conductor which put to the metal part of the bulb-base.
In the compact selfballasted fluorescent lamp according to the eighth aspect of the invention, in addition to an effect of any one of the first to the seventh aspects of the invention, since at least the node of the bulb-base is made of a metal which has high thermal conductivity, the radiating effect is further heightened by conducting heat from the thermal conductor to the bulb-base.
In addition to the feature of any one of the first to eighth aspects of the invention, the compact selfballasted fluorescent lamp according to the ninth aspect of the invention is characterized by that a fine tube enclosing an amalgam is mounted on the tube end of the compact selfballasted fluorescent lamp, and that the thermal conductor is able to contact with the fine tube by being filled through through-holes defined in the circuit board.
The through-hole defined in the circuit board, that is a hole through which a fine tube is penetrable from the back of the board, is desirable to be formed a little bigger than a fine tube outer diameter.
The term xe2x80x9cfine tube and the thermal conductor contact each otherxe2x80x9d means that the end of the fine tube may contact with the circuit board surface, or it may penetrate through the hole in the circuit board to the bulb-base side. In short, the thermal conductor and the fine tube may contact each other.
In the compact selfballasted fluorescent lamp according to ninth aspect of the invention, in case of that the thermal conductor and the fine tube contact each other, since heat from the circuit components is conducted to the fine tube via the thermal conductor, the amalgam is wormed quickly, and the mercury evaporates at an early stage right after lighting operation, so that the luminous flux start-up characteristic can be improved.
A compact selfballasted fluorescent lamp according to the tenth aspect of the invention, comprising a fluorescent arc tube forming a crooked discharge path, a housing comprised of a first end portion open to be fit thereon with a bulb-base, a middle portion and a second end portion open to be mounted thereto with the fluorescent, a light circuit module provided with two ore more circuit components including an electrolytic capacitor which constitutes a light circuit for lighting the fluorescent arc tube on and a circuit board to which these circuit components are mounted, and is accommodated in a housing, and a thermal conductor which is filled in the housing so as to contact with the inner wall of the housing above the upper side of the circuit board of the lighting circuit module, thereby covering the circuit components of the lighting circuit modules excepting at least a safety valve of an electrolytic capacitor.
The term xe2x80x9cportion excepting a safety valve of an electrolytic capacitorxe2x80x9d means a portion of the electrolytic capacitor shaped in approximately cylindrical excepting its bulb-base side, which indicates a housing for covering impregnated element and a sealing portion for sealing the housing formed on the fluorescent arc tube side, and which may also contain lead wires lead out of the sealing portion.
Like a conventional technique wherein all the circuit components mounted on the bulb-base side among the circuit components mounted on the circuit board are covered by synthetic resin material, in case of keeping lighting the lamp at high temperature to the extent that the temperature in the housing exceeds a rated acceptable temperature or in a housing of being applied a voltage at the life last stage when inner electrolysis liquid vaporizes and decreases, the electrolytic capacitor tends to open the safety valve. However, if the safety valve of the electrolytic capacitor is completely covered by synthetic resin, the safety valve will not be opened, so that the electrolytic capacitor would explode. Therefore, the thermal conductor is needed to cover a portion excepting the safety valve of the electrolytic capacitor.
In the compact selfballasted fluorescent lamp according to the tenth aspect of the invention, since the thermal conductor covers a portion excepting a safety valve of the electrolysis capacitor, the safety valve is able to be opened in case of that the lamp is kept lighted at high temperature that exceeds the rated acceptable temperature of the electrolysis capacitor or at the life last stage when the electrolysis liquid of the electrolysis capacitor decreases, thereby it is able to prevent a risk such as a burst.
In addition to the feature of any one of the first to tenth aspects of the invention, the compact selfballasted fluorescent lamp according to the eleventh aspect of the invention is characterized by that the fluorescent arc tube holder mounted on the second end portion of the housing is made of synthetic resin containing at least flame retardant.
Although synthetic resin containing flame retardant also contains a bromine compound to enhance the flame retardance, it generates gases of halogen such as bromine in response to the heat and the ultraviolet rays from the fluorescent arc tube. When the halogen gases encroach on an inside the lighting circuit module through the gap between the circuit board and the rubber packing as a sealing metal of the circuit board, it will corrode the electrolytic capacitor and causes problems. Therefore, it is desirable not to use synthetic resin containing flame retardant for a compact selfballasted fluorescent, which is lighted at a high temperature as much as possible. However, such synthetic resin which does not contain aflame retardant is expensive, so that it will make the compact selfballasted fluorescent lamp expensive. In the present invention, a rubber packing portion as a sealing material is covered completely by the thermal conductor in order to seal the gap between the fluorescent arc tube holder and the circuit board, thereby it is able to prevent the invasion of halogen gases into the lighting circuit module.
In the compact selfballasted fluorescent lamp according to the eleventh aspect of the invention, in addition to the operations according to the first to the tenth aspects of the invention, it is able to provide an inexpensive compact selfballasted fluorescent lamp by using synthetic resin containing flame retardant.
In addition to the feature of any one of the first to eleventh aspects of the invention, the compact selfballasted fluorescent lamp according to the twelfth aspect of the invention is characterized by that all tube ends of the compact selfballasted fluorescent lamp are placed so as to face the circuit board.
Although in such a conventional compact selfballasted fluorescent lamp, one integrated crooked tube is accommodated in a glove, positions or configurations of the tube ends are not practically specified. Furthermore, in previous well-known techniques, a fluorescent arc tube was not thinned to the extent that the tube-wall load rises, and the miniaturization of whole body was not advanced, so that it did not get so high temperature as to cause problems to the lighting circuit module by the heat of the fluorescent arc tube.
In the compact selfballasted fluorescent lamp according to the twelfth aspect of the invention, since all tube ends of the fluorescent arc tube are placed so as to face the circuit board, the lighting circuit module which is placed in proximity to the tube ends supporting electrodes thereon tend to be affected by the heat, however, it is able to prevent from getting high temperature inside the housing by dissipating heat via the thermal conductor filled in the housing.
A luminaire according to the thirteenth aspect of the invention is characterized by that it is comprised of the compact selfballasted fluorescent lamp according to any one of the first to the twelfth aspects of the invention and a luminaire main body to which the compact selfballasted fluorescent lamp is mounted.
In the luminaire according to the thirteenth aspect of the invention, it is able to provide a luminaire which is provided with a compact selfballasted fluorescent lamp having a function of any one of the first to the twelfth aspect of the invention.